I'm considering using kerfing to set rocker into a 25mm PVC foam blank, for my next HF board.
The idea is:
1) Cut several deep grooves in the top surface, side to side, in the area where rocker is required.
2) Fill grooves with epoxy/micro-balloon mix
3) Set desired rocker, wipe away excess and leave to set.
4) Cut/shape desired shape from the preformed blank.
Some ball park values:
6 grooves, 1mm wide, 20mm deep, spacing around 100mm. The aim is about 10cm of rocker over the 1st 5-600mm of the board.
The main advantage of setting the rocker before lamination (rather that setting it during lamination, on a rocker table) is the top and bottom surfaces of the core don't change length as vac bagging pressure is applied. ie your nicely squeeged flat laminate is not disturbed.
Before jumping down this route I'd be interested to hear if this has been tried before and any real or perceived issues.
The two slight issues i can foresee are
a) The rocker curve may come out a little bit 'digital'. I can't see this being much an issue as it hopefully won't be in the water most of the time and its only really there to limit pearling on touchdowns.
b) There will be discontinuities in the core stiffness at the kerf lines. I can see this might be an issue if board was being designed to flex ...but the intention is to be stiff..top and bottom will include carbon. The kerf lines may also act as stress raisers but most the the (HF) stresses should be well behind them.
Comments & suggestions welcome....